The representation of the horizontal meridian in the primary visual cortex.

The authors report the findings of two patients that confirm the location of the horizontal meridian in the human visual cortex. The first patient had an inferior quadrant defect with a band of horizontal meridian sparing. Magnetic resonance imaging showed a lesion concentrated along the medial striate cortex. The second patient had a homonymous horizontal defect that resulted from removal of an arteriovenous malformation located in the lateral striate cortex. The findings of these two patients demonstrate that the horizontal meridian is represented at the calcarine fissure base in the primary visual cortex.